Illumination field blending for use in subtitle projection systems

ABSTRACT

A projection system that projects a text or subtitle box onto an image minimizes the contrast between the text box and the image. A transition region surrounding the text box minimizes visual disruption to the image onto which the text box is projected. The positions of optical elements of a text projector enable the text box to gradually fade out. The text projector has a lamp that defines an object plane and a light path modifier. The light path modifier is offset from the object plane, toward the lamp to blend the borders of the text box into the image projected by an image projector.

TECHNICAL FIELD

This invention relates to image projection systems that superimpose textonto a screen with an image of a projected film.

BACKGROUND OF THE INVENTION

Subtitles or text images that are projected onto a screen from a filmhaving a movie or other image are commonly laser etched into the filmitself. Subtitles etched onto film can be difficult to see, particularlyif at any time the images in the film have a color that matches thecolor of the subtitles. The film image can temporarily camouflage thesubtitles. In addition, because the subtitles are etched onto the filmitself, a unique and separate film must be made having subtitles in eachdesired language.

To make subtitles more visible and to avoid the need to alter the filmitself, a projection system which projects one image onto another imagemay be used to project subtitles onto another image on a screen. Such aprojection system has a first projector that projects the movie or otherimages onto a screen and a second projector that projects a text boxcontaining subtitles onto the screen. The second projector, instead ofprojecting subtitles that have been etched onto film, may projectdigital images from a compact disc. These digital images are clearerthan text that has been etched onto film. In addition, a compact discmay have the subtitles in a variety of languages, making internationaldistribution of movies simpler because the film can be distributed inits original form.

A disadvantage of using such a text projection system is that the textbox sharply transitions from light to dark, making the border of thesubtitle image sharp and clearly visible on the image. This sharptransition creates a sharply distinct box on the image, cutting outwhatever portion of the image that would otherwise be seen where the boxis located. Such a text box prevents the image from gradually blendinginto the text.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a projector that projects atext box with a fade out transition region to enable a text box toappear to gradually fade out into the other image.

The projection system of the present invention projects a text box witha fade out transition region that minimizes visual disruption to theimage onto which the text box is projected. The fade out transitionregion is created by the position of the optical elements of a textprojector, as discussed below. The projection system includes an imageprojector and a text projector. The image projector projects an imageonto a screen, and the text projector projects text or subtitles onto aportion of the image. The text or subtitles are projected in a text box.

The text projector has a light source or lamp adapted to project lightas a text box. The text projector also has a light path modifierpositioned to receive light from the light source. In one embodiment,the light path modifier is an integrator tunnel with reflective walls.In another embodiment, the light path modifier is a pair of fly eyepanels. The text projector further includes a relay lens that transmitslight in the form of a text box from the light path modifier to adisplay device. The display device may be transmissive or reflective. Aprojection lens receives light from the display device and is positionedto project a text box onto the image projected by the image projector.The text projector preferably has an optional pair of condensing lensespositioned to condense light and direct it from the light path modifierto the relay lens. A single condensing lens may also be used.Alternatively, the relay lens may function as the condensing lens.

The sharpness of the borders of the text box are determined by theplacement of the light path modifier relative to an object plane. Theposition of the object plane is defined by the position of the relaylens. Projectors which project a sharply defined text box onto anotherimage have a relay lens that defines an object plane at the exit end ofa light tunnel or other light path modifier. In order to decrease thesharpness of the borders of the text box, the exit end of the light pathmodifier is sufficiently offset from the object plane so that thecontrast between the text box and the image projected by the imageprojector is diminished. The light path modifier may also besufficiently offset so that the image projected by the image projectoris at least partially visible through the text box and so that the textbox has a fade out transition region. The borders of such a text boxwill blend into the image projected by the image projector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the projection system with an image projectorand a text projector projecting onto a screen.

FIG. 2A illustrates a first example of a text box projected onto anotherimage as it would appear on a screen when a prior art system isutilized.

FIG. 2B illustrates a first example of a text box projected onto anotherimage as it would appear on a screen when a system is used in accordancewith the present invention.

FIG. 3A illustrates a second example of a text box projected ontoanother image as it would appear on a screen when a prior art system isutilized.

FIG. 3B illustrates a second example of a text box projected ontoanother image as it would appear on a screen when a system is utilizedin accordance with the present invention.

FIG. 4A is a schematic of the elements of the text projector of anembodiment of the present invention with an integrator tunnel

FIG. 4B is a schematic of the elements of the text projector of anembodiment of the present invention with a pair of fly eye panels.

FIG. 5A is a schematic of the optical architecture and the relationshipof the object plane and the display device, as a function of theplacement of the light path modifier before the light path modifier isoffset from the object plane.

FIG. 5B is a schematic of the optical architecture and the relationshipof the object plane and the display device, as a function of theplacement of the light path modifier after the light path modifier isoffset from the object plane.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Different embodiments of the present invention, described by way ofexample, project an image and a text box, the text box having bordersthat enable the image to be seen along the borders. Skilled persons willreadily appreciate that the present invention can be used in anyprojection system that projects one image onto another.

One embodiment of a projection system 10 is shown in FIG. 1, with animage projector 20 and a text projector 30. Image projector 20 projectsan image 120 onto a screen 100 and text projector 30 projects a smallerimage, as text 132 in a text box 130, onto the screen 100. Together,text box 130 and image 120 form a composite image 110.

FIGS. 2A and 3A illustrate text boxes 130 projected by a text projector30 of the prior art as the text boxes 130 would appear in compositeimage 110. Text boxes 130 of the prior art have borders 134 that aresharply defined, making text box 130 distinct from image 120. The sharpdefinition of border 134 completely blocks out precisely as much ofimage 120 as overlaps text box 130. Text boxes 130 of the prior art alsoprevent image 120 from gradually blending into text 132.

FIGS. 2B and 3B illustrate the appearance of text boxes 130 when lightis transmitted onto a screen through use of an embodiment of the presentinvention. Text boxes 130 of FIGS. 2B and 3B have a fade out transitionregion 136 that gradually fades out completely at border 134 of text box130, enabling more of image 120 to be viewed than text boxes 130delivered in accordance with the prior art, as shown in FIGS. 2A and 3A.Fade out transition region 136 enables text box 130 to blend with image120, making text box 130 less visually disruptive to composite image110.

FIGS. 4A and 4B are schematic views of the elements required for textprojector 30 of two different embodiments of a projection system 10.Text projector 30 has a light source or lamp 40 adapted to project lightto display text 132 and text box 130. Text projector 30 also has a lightpath modifier. In the embodiment shown in FIG. 4A, the light pathmodifier is an integrator tunnel 50 with an entry end 52 and an exit end54. Integrator tunnel 50 is a tunnel with reflective walls as disclosedin U.S. Pat. No. 5,625,738, which is incorporated herein by reference.

Integrator tunnel 50 is positioned to receive light from light source 40at entry end 52. Integrator tunnel 50 redistributes light from lightsource 40 so that, at exit end 54, the light is uniformly distributed ina shape matching the that of text box 130. In the embodiment shown inFIG. 4B, the light path modifier is a pair of fly eye panels 50′, eachof which corresponds to an array of small lenses, with a first fly eyepanel 52′ and a second fly eye panel 54′.

Text projector 30 further includes a relay lens 70 positioned to receivelight from light path modifier 50 or 50′ and to transmit light to adisplay device 80. As shown in FIG. 4B, the text projector preferablyincludes a pair of condensing lenses 62, 64. A single condensing lensmay also be used. Condensing lenses 62, 64 are positioned to direct andcondense light from light path modifier 50 or 50′ to relay lens 70.Condensing lenses 60 operate to condense light so that display devicecan be smaller, reducing the overall cost of text projector 30. In analternative embodiment, the text projector has no condensing lenses andrelay lens 70 operates both as a relay lens and a condensing lens, asshown in FIG. 4A.

Display device 80 receives light in the shape of text box 130 as it isto be projected on screen 100. Display device 80 may be transmissive orreflective. For example, display device 80 may be a transmissive LCDpanel or a reflective array of mirrors. A projection lens 90 ispositioned to receive light transmitted or reflected by display device80. The focus of text 132 in text box 130 is determined by the positionof projection lens 90 relative to display device 80. Projection lens 90is also positioned to superimpose text box 130 onto image 120, formingcomposite image 110.

As shown in FIGS. 5A and SB, the position of relay lens 70 defines theposition of an object plane 44. FIG. SA shows exit end 54 of integratortunnel 50 at object plane 44. In similar projectors that utilize fly eyepanels, second fly eye panel 54′ is at object plane 44. Text projector30, configured as shown in FIG. 5A with exit end 54 or second fly eyepanel 54′ at object plane 44, projects a sharply defined image, with aborder that abruptly transitions from image 120.

FIG. 5B shows an embodiment of the present invention with an integratortunnel 50 as the light path modifier. Exit end 54 is sufficiently offsetfrom object plane 44 and away from relay lens 70 such that the lightfrom light source 40 is concentrated on the center of display device 80and increasingly diffuse as the light approaches the edges of displaydevice 80. The same effect may be achieved by offsetting exit end 54from object plane 44 towards relay lens 70. The decrease in lightconcentration from the center of text box 130 to borders 134 of text box130 minimizes the contrast between text box 130 and image 120. Statedotherwise, exit end 54 of integrator tunnel 50 is sufficiently offsetfrom object plane 44 to enable image 120 to be at least partiallyvisible through text box 130 at fade out transition region 136. Borders134 of text box 130 projected by text projector as shown in FIG. 5Bblend into image 120 along fade out transition region 136. Such agradual transition causes less visual disruption to composite image 110while still enabling text 132 to be completely legible. Similarly, inembodiments containing fly eye panels, front fly eye panel 54 is offsetfrom object plane 44 as described above for exit end 54.

There are several steps involved in a method for projecting compositeimage 110 that minimizes the contrast at the transition from text box130 around text 132 to image 120. After obtaining image projector 20 andobtaining text projector 30 with optical elements adapted to projecttext 132 in a text box 130, as described above, the optical elements aremodified. More particularly the optical elements of text projector 30are adjusted so that exit end 54 or front fly eye panel 54 is offsetfrom object plane 44 away from relay lens 70 from exit end 54 or frontfly eye panel 54. Alternatively, exit end 54 or front fly eye panel 54may be offset toward object plane 44 toward relay lens 70.

As described above in connection with FIGS. 4A and 4B, adjusting theoptical elements involves identifying the position of object plane 44 asdefined by the position of relay lens 70 and positioning light pathmodifier 50, 51′ relative to object plane 44 so that the light pathmodifier 50, 50′ is offset from object plane 44. The light path modifier50, 50′ is offset from object plane 44 away from relay lens 70sufficiently to diffuse light at borders 134 and concentrate lighttowards text 132 in text box 130 and to display device 80, therebydecreasing the sharpness of borders 134 so that contrast between textbox 130 and image 120 is diminished. As discussed above, a similareffect is achieved by offsetting light path modifier 50 from objectplane 44 toward relay lens 70.

It will be obvious to those having skill in the art that many changesmay be made to the details of the above-described embodiments of thisinvention without departing from the underlying principles thereof. Thescope of the present invention should, therefore, be determined only bythe following claims.

What is claimed is:
 1. In a projection system that includes an image projection system adapted to project an image, a text projection system which is adapted to project text in a text box onto the image projected by the image projection system, the text projection system comprising: a light source adapted to project light to display text in a text box; a light path modifier positioned to receive light from the light source; a relay lens positioned to receive light from the light path modifier; a display device positioned to receive the light from the relay lens; and a projection lens positioned to receive the light from the display device and to direct the light so as to superimpose the text box onto the image projected by the image projection system, wherein the relay lens defines the position of an object plane and wherein the light path modifier is sufficiently offset from the object plane to decrease the sharpness of borders of the text box so that contrast between the text box and the image projected by the image projection system is diminished.
 2. The image projection system of claim 1, in which the light path modifier is offset from the object plane toward the light source.
 3. The image projection system of claim 1, in which the light path modifier is offset from the object plane away from the light source.
 4. The image projection system of claim 1, in which the light path modifier is sufficiently offset from the object plane to enable the image projected by the image projection system to be at least partially visible through the text box.
 5. The image projection system of claim 1, in which the position of the light path modifier causes the light to be concentrated towards the center of the text box and increasingly diffuse approaching the edges of the text box enabling the borders of the text box to be unfocused and yet the text in the text box is completely legible.
 6. The image projection system of claim 1, in which the relay lens condenses light from the light path modifier.
 7. The image projection system of claim 1, in which the projection system includes a pair of condensing lenses, the pair being positioned to receive the light from the light path modifier and to direct the light to the relay lens.
 8. The image projection on system of claim 1, in which the light path modifier is an integrator tunnel.
 9. The image projection system of claim 1, in which the light path modifier is a pair of fly eye panels.
 10. The image projection system of claim 1, in which the display device is transmissive.
 11. The image projection system of claim 1, in which the display device is reflective.
 12. A projection system, comprising: an image projection system adapted to project an image; and a text projection system adapted to project text in a text box, wherein the text projection system comprises a light path modifier positioned to receive light from a light source and to direct the light to a relay lens, the relay lens being positioned to transmit the light toward a display device positioned to direct the light to a projection lens, wherein the projection lens is positioned to superimpose the text box onto the image projected by the image projection system, and wherein the relay lens defines the position of an object plane and wherein light path modifier is sufficiently offset from the object plane to decrease the sharpness of borders of the text box so that contrast between the text box and the image projected by the image projection system is diminished.
 13. The image projection system of claim 12, in which the light path modifier is offset from the object plane toward the light source.
 14. The image projection system of claim 12, in which the light path modifier is offset from the object plane away from the light source.
 15. The image projection system of claim 12, in which the light path modifier is sufficiently offset from the object plane to enable the image projected by the image projection system to be at least partially visible through the text box.
 16. The image projection system of claim 12, in which the position of the light path modifier causes the light to be diffused at the borders of the text box.
 17. The image projection system of claim 12, in which the relay lens also operates as a condensing lens.
 18. The image projection system of claim 12, in which the projection system includes a pair of condensing lens, the pair being positioned to receive light from the light path modifier and to direct the light to the relay lens.
 19. The image projection system of claim 12, in which the light path modifier is an integrator tunnel.
 20. The image projection system of claim 12, in which the light path modifier is a pair of fly eye panels.
 21. The image projection system of claim 12, in which the display device is transmissive.
 22. The image projection system of claim 12, in which the display device is reflective.
 23. A method for projecting an image with subtitles that minimizes the contrast at a transition from a text box around the subtitles to a projected image, comprising: obtaining an image projection system adapted to project an image; obtaining a text projection system having optical elements adapted to project light to display the text in the text box; and adjusting the optical elements of the text projection system so that the light projected by the text projection system is diffused along borders of the text box.
 24. The method of claim 23, in which the texe projection system includes: a light surce adapted to project light to display text in a text box; a light path modifier being positioned to receive a light at its entry end from the light source; a relay lens being positioned to receive the light from the light path modifier; a display device positioned to receive the light transmitted from the relay lens; and a projection lens positioned to receive the light from the display device and to direct the light so as to superimpose the text box onto the image projected by the image projection system.
 25. The method of claim 24 further comprising: identifying the position of an object plane as defined by the relay lens; and positioning the light path modifier relative to the object plane such that the light path modifier is sufficiently offset from the object plane to decrease the sharpness of borders of the text box so that contrast between the text box and the image projected by the image projection system is diminished.
 26. The method of claim 25, in which the light path modifier is sufficiently offset from the object plane to enable the image projected by the image projection system to be visible through the text box. 